bfd_check_format: ignore errors from coff_real_object_p

bfd_check_format: ignore errors from coff_real_object_p

Since 1993-11-05 git commit c188b0bec3b, bfd_check_format has failed
if any of the target object_p functions returns false with any error
but bfd_error_wrong_format.  That's just weird.  There is really no
reason why coff_real_object_p should be fixed to only return that
error instead of numerous other possible errors.  Even an out of
memory condition for one target doesn't necessarily mean other targets
can't match, assuming the failing target nicely returns all memory it
might have used.

	* format.c (bfd_check_format_matches): Ignore bfd_error on target
	match failures.  Don't init to bfd_error_wrong_format before
	calling _bfd_check_format.